(define-syntax define-values
    (syntax-rules ()
      ((_ () body)
       (call-with-values (thunk body) void))
      ((_ (var . vars) body)
       (begin
         (define var (call-with-values (thunk body) list))
         (define-values vars (apply values (cdr var)))
         (set! var (car var))))
      ((_ var body)
       (define var (call-with-values (thunk body) list)))))